This invention relates to apparatus for sensing and displaying mechanical position information, and more particularly to such apparatus that utilizes a passive fiber optic transmission system with means for testing its continuity to enhance reliablitiy.
Previous systems for sensing the mechanical information of aircraft components, such as the relative positive of swing wings, landing gear, etc., utilized mechanically actuated switches and/or electromagnetic influenced proximity switches. These systems may be referred to as "active" systems in that they require transmission of electrical signals from the mechanical component to a remotely located electrical processor, which either converted the sensed mechanical condition provided by the electrical signal to a visible display, or else provided logic inputs to system control functions by computer processing of the logic inputs.
Both of these approaches required the use of electrical power and a suitable grounding system for proper operation, and, therefor, required extensive design constraints to prevent electromagnetic interferenc, radio frequency interference, and/or electromagnetic pulse interference, from adversely effecting their proper operation.
In addition mechanical acutated electrical switches are very susceptible to electrical point bounce, electrical contact resistance, and mechanical failure problems. Electromagnetic proximity switches usually contain integrated circuits which are relatively expensive, and will fail in extreme temperature environments frequently encountered in military aircraft flight operations.